In the previous study, numerical simulations were done for countercurrent gas-liquid flows in a vertical pipe by using a volume of fluid method (VOF) implemented in the CFD software, FLUENT6.3.26, to evaluate countercurrent flow limitation (CCFL) at the lower end of steam generator U-tubes The simulated CCFL characteristics agreed well with air-water experimental data but flooding in simulations appeared at the upper end of the vertical pipe, which meant that CCFL at the upper end was too rigorously simulated To avoid flooding at the upper end, therefore, water was supplied through the pipe wall simulating condensation on the inner surface and flooding near the lower end was simulated, but it was flooding in the pipe So in this study, the effect of the contact angle of water was evaluated, because the contact angle becomes small when the inner surface of the pipe is wet with a thin water layer With small contact angles, flooding at the lower end was successfully simulated
